Zoledronic acid for the prevention of bone loss in postmenopausal women with low bone mass: a randomized controlled trial.

Objective: To evaluate the efficacy of zoledronic acid in the prevention of bone loss in postmenopausal women with low bone mass.
Methods: In this 2-year, randomized, multicenter, double-blind, placebo-controlled study, postmenopausal women with low bone mass were selected randomly to receive either zoledronic acid 5 mg intravenously at randomization and at month 12 (zoledronic acid 2 x 5 mg), zoledronic acid 5 mg intravenously only at randomization and placebo at month 12 (zoledronic acid 1 x 5 mg), or placebo at randomization and at month 12 (placebo). The primary efficacy endpoint was the percentage change in lumbar spine bone mineral density (BMD) (lumbar spine BMD) at month 24 relative to baseline.
Results: Both zoledronic acid 2 x 5 mg and zoledronic acid 1 x 5 mg regimens significantly increased mean lumbar spine BMD compared with placebo at month 24 (5.18% and 4.42% compared with -1.32%, respectively, both P<.001). Similarly, significantly greater increases for both zoledronic acid regimens relative to placebo were observed for lumbar spine BMD at month 12 and for BMD at the proximal femur sites (total hip, femoral neck, trochanter) at month 12 and 24 (all P<.001). Both zoledronic acid regimens significantly reduced bone turnover markers over time relative to placebo (all P<.001), although changes with zoledronic acid 2 x 5 mg regimen were sustained greater during the second year relative to zoledronic acid 1 x 5 mg. The overall incidence of adverse events and serious adverse events were similar across all treatment groups.
Conclusion: Both once-yearly dosing and a single dose of intravenous zoledronic acid 5 mg prevented bone loss for 2 years and were well-tolerated in postmenopausal women with low bone mass.
Clinical Trial Registration: ClinicalTrials.gov, www.clinicaltrials.gov, NCT00132808.
Level of Evidence: I.